An ESR study of the reaction of silver atoms with B2F4 under matrix isolation conditions

Abstract

Diboron tetrafluoride has been found by ESR to complex with silver atoms when the species are deposited together in hydrocarbon matrices at 77 K in a rotating cryostat. The major feature in the ESR spectra of the deposit in adamantane and cyclohexane matrices (Ag ∶ B₂F₄ ∶ matrix ratio of ∼1 ∶ 5 ∶ 500) was an almost isotropic set of two doublets of 13 (or possibly 15)-line multiplets. The two sets of doublets arise from the almost equally abundant ¹⁰⁷Ag and ¹⁰⁹Ag isotopes with I = 1/2. The multiplets on each silver line indicate hyperfine interaction with either four equivalent ¹¹B nuclei (I = 3/2) or two equivalent ¹¹B nuclei and four equivalent ¹⁹F nuclei. Multiplets from the less abundant ¹⁰B isotope (19.8%, I = 3) were not resolvable. The almost isotropic multiplets are best simulated as axial spectra with |A_∥|(¹¹B) = 17.5 MHz and |A_⊥|(¹¹B) = 14.1 MHz and A_iso(¹⁰⁷Ag) = 1371.0 MHz. The complex is either [Ag(B₂F₄)₂] or [Ag(B₂F₄)]. Assuming that A_∥ and A_⊥ are both positive, the total spin density is calculated to be 0.85 in [Ag(B₂F₄)₂] and 0.80 in [Ag(B₂F₄)]. The most likely structures together with density function calculations on these two possibilities are discussed.